A thermoplastic polyurethane elastomer has been conventionally used in various fields such as hoses, belts, electric wires, cables, pipes, soles and various types of molded articles, taking advantage of its excellent mechanical strength and wear resistance. Particularly, a resin which is improved in molding ability and water resistance obtained by alloying an ethylene copolymer such as an ethylene-vinyl acetate copolymer (EVA) and a thermoplastic polyurethane elastomer (Patent document 1) is used. However, the thermoplastic polyurethane elastomer, which consists of movable long chain parts called a soft segment and extremely high crystalline parts called a hard segment, has poor compatibility with other resins. Therefore, it has a disadvantage that the compatibility with ethylene polymers and ethylene copolymers is insufficient.
Furthermore, the thermoplastic resin composition having the thermoplastic polyurethane elastomer and the ethylene copolymer as the main components has a disadvantage of being poor in flame retardancy. This disadvantage is improved by adding a metallic hydrate such as magnesium hydrate (Patent document 2). However, the thermoplastic resin composition having the thermoplastic polyurethane elastomer and the ethylene (co)polymer as the main components is noncompatible. or poorly compatible on its own. Therefore, the compatibility gets worse and worse by using a large amount of inorganic substances such as a metallic hydrate, and also workability, surface properties of resin and physical properties or the like deteriorate and the flame retardancy thereof was not sufficient.
In addition, resin compositions wherein compounds containing nitrogen and/or phosphor such as melamine phosphate, melamine polyphosphate and condensed phosphate ester were added to the thermoplastic polyurethane elastomer to impart flame retardancy are known (Patent document 3). However, in this case, the flame-retardant mechanism is not the one wherein the flame retardancy is provided by forming a surface intumescent layer so as to suppress a diffusion of the decomposition products and heat transmission produced when burned. Moreover, there is no description in the specification suggesting that the compatibility of the above resin composition was improved.
On the other hand, an invention wherein a specific phosphate compound and a phosphate ester flame retardant were added to the thermoplastic polyurethane elastomers in combination was disclosed (Patent document 4). However, this invention concerns a fire-retardant sealing agent which is completely different in use from electric wires and cables or the like. Moreover, there is no description suggesting that the compatibility and flame retardancy of the resin composition having the thermoplastic polyurethane elastomer and the ethylene copolymer as the main components were improved.